Functions in Python.ipynb

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   "source": [
    "## Function in Python\n",
    "\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Defining the Function"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "def print_greeting():\n",
    "    print(\"Hello World\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hello World\n"
     ]
    }
   ],
   "source": [
    "print_greeting()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The functino header always starts with the \"def\" keyword that indicates that this is a Function Defination.   \n",
    "def unction_name(arrgument):\n",
    "            #Function_Body\n",
    "            \n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Print Vs. Return in Functions"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Heare are two valid functions. One returns a value and one simply prints a value, without returning anything."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [],
   "source": [
    "# this prints something, but does not return anything\n",
    "def show_plus_ten(num):\n",
    "    print(num + 10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "13\n"
     ]
    }
   ],
   "source": [
    "show_plus_ten(3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [],
   "source": [
    "# this returns something\n",
    "def add_ten(num):\n",
    "    return(num + 10)"
   ]
  },
  {
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   "execution_count": 6,
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   "source": [
    "add_ten(4)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Volume of a cylinder: formula  = pi*h**r**2\n",
    "def cylinder_volume(height , radius):\n",
    "    pi = 3.14159\n",
    "    return height*pi*radius**2"
   ]
  },
  {
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   "execution_count": 8,
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   "source": [
    "cylinder_volume(5 , 3)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Default Arguments\n",
    "We can add default arguments in a function to have default values for parameters that are unspecified in a function call."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [],
   "source": [
    "def cylinder_volume(height , radius = 5):\n",
    "    pi  = 3.14\n",
    "    return height * pi * radius**2"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "In the example above, radius is set to 5 if that parameter is omitted in a function call. If we call cylinder_volume(10), the function will use 10 as the height and 5 as the radius. However, if we call cylinder_volume(10, 7) the 7 will simply overwrite the default value of 5."
   ]
  },
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   "source": [
    "cylinder_volume(10,7)"
   ]
  },
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   "execution_count": 11,
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   "source": [
    "cylinder_volume(height=10, radius=7) "
   ]
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Nested Function\n",
    "In this exercise, inside a function three_shouts(), you will define a nested function inner() that concatenates a string object with !!!. three_shouts() then returns a tuple of three elements, each a string concatenated with !!! using inner(). Go for it!"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Complete the function header of the nested function with the function name inner() and a single parameter word.\n",
    "\n",
    "Complete the return value: each element of the tuple should be a call to inner(), passing in the parameters from three_shouts() as arguments to each call"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "('a!!!', 'b!!!', 'c!!!')\n"
     ]
    }
   ],
   "source": [
    "# Define three_shouts\n",
    "def three_shouts(word1, word2, word3):\n",
    "    \"\"\"Returns a tuple of strings\n",
    "    concatenated with '!!!'.\"\"\"\n",
    "\n",
    "    # Define inner\n",
    "    def inner(word):\n",
    "        \"\"\"Returns a string concatenated with '!!!'.\"\"\"\n",
    "        return word + '!!!'\n",
    "\n",
    "    # Return a tuple of strings\n",
    "    return (inner(word1) , inner(word2) , inner(word3))\n",
    "\n",
    "# Call three_shouts() and print\n",
    "print(three_shouts('a', 'b', 'c'))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Problem\n",
    "#Let's once again work further on your mastery of scope! In this exercise, you will use the keyword \"nonlocal\" within a nested function to alter the value of a variable defined in the enclosing scope."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Hint\n",
    "#Assign to echo_word the string word, concatenated with itself.\n",
    "#Use the keyword nonlocal to alter the value of echo_word in the enclosing scope.\n",
    "#Alter echo_word to echo_word concatenated with '!!!'.\n",
    "#Call the function echo_shout(), passing it a single argument 'hello'.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "hellohello\n",
      "hellohello!!!\n"
     ]
    }
   ],
   "source": [
    "# Define echo_shout()\n",
    "def echo_shout(word):\n",
    "    \"\"\"Change the value of a nonlocal variable\"\"\"\n",
    "    \n",
    "    # Concatenate word with itself: echo_word\n",
    "    echo_word = word*2\n",
    "    \n",
    "    # Print echo_word\n",
    "    print(echo_word)\n",
    "    \n",
    "    # Define inner function shout()\n",
    "    def shout():\n",
    "        \"\"\"Alter a variable in the enclosing scope\"\"\"    \n",
    "        # Use echo_word in nonlocal scope\n",
    "        nonlocal echo_word\n",
    "        \n",
    "        # Change echo_word to echo_word concatenated with '!!!'\n",
    "        echo_word = echo_word+'!!!'\n",
    "    \n",
    "    # Call function shout()\n",
    "    shout()\n",
    "    \n",
    "    # Print echo_word\n",
    "    print(echo_word)\n",
    "\n",
    "# Call function echo_shout() with argument 'hello'\n",
    "echo_shout('hello')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "BEGIN: REPORT\n",
      "\n",
      "name: luke\n",
      "affiliation: jedi\n",
      "status: missing\n",
      "\n",
      "END REPORT\n",
      "\n",
      "BEGIN: REPORT\n",
      "\n",
      "name: anakin\n",
      "affiliation: sith lord\n",
      "status: deceased\n",
      "\n",
      "END REPORT\n",
      "\n",
      "BEGIN: REPORT\n",
      "\n",
      "name: luke\n",
      "affiliation: jedi\n",
      "status: missing\n",
      "\n",
      "END REPORT\n",
      "\n",
      "BEGIN: REPORT\n",
      "\n",
      "name: anakin\n",
      "affiliation: sith lord\n",
      "status: deceased\n",
      "\n",
      "END REPORT\n"
     ]
    }
   ],
   "source": [
    "# Define report_status\n",
    "def report_status(**kwargs):\n",
    "    \"\"\"Print out the status of a movie character.\"\"\"\n",
    "\n",
    "    print(\"\\nBEGIN: REPORT\\n\")\n",
    "\n",
    "    # Iterate over the key-value pairs of kwargs\n",
    "    for key, value in kwargs.items():\n",
    "        # Print out the keys and values, separated by a colon ':'\n",
    "        print(key + \": \" + value)\n",
    "\n",
    "    print(\"\\nEND REPORT\")\n",
    "# Define report_status\n",
    "def report_status(**kwargs):\n",
    "    \"\"\"Print out the status of a movie character.\"\"\"\n",
    "\n",
    "    print(\"\\nBEGIN: REPORT\\n\")\n",
    "\n",
    "    # Iterate over the key-value pairs of kwargs\n",
    "    for key, value in kwargs.items():\n",
    "        # Print out the keys and values, separated by a colon ':'\n",
    "        print(key + \": \" + value)\n",
    "\n",
    "    print(\"\\nEND REPORT\")\n",
    "\n",
    "# First call to report_status()\n",
    "\n",
    "report_status(name =\"luke\" , affiliation  = 'jedi' , status = \"missing\")\n",
    "# Second call to report_status()\n",
    "report_status(name=\"anakin\", affiliation=\"sith lord\", status=\"deceased\")\n",
    "# First call to report_status()\n",
    "\n",
    "report_status(name =\"luke\" , affiliation  = 'jedi' , status = \"missing\")\n",
    "# Second call to report_status()\n",
    "report_status(name=\"anakin\", affiliation=\"sith lord\", status=\"deceased\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "In this exercise, we will generalize the Twitter language analysis that you did in the previous chapter. You will do that by including a default argument that takes a column name."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
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     "output_type": "stream",
     "text": [
      "{'en': 97, 'et': 1, 'und': 2}\n",
      "{'<a href=\"http://twitter.com\" rel=\"nofollow\">Twitter Web Client</a>': 24, '<a href=\"http://www.facebook.com/twitter\" rel=\"nofollow\">Facebook</a>': 1, '<a href=\"http://twitter.com/download/android\" rel=\"nofollow\">Twitter for Android</a>': 26, '<a href=\"http://twitter.com/download/iphone\" rel=\"nofollow\">Twitter for iPhone</a>': 33, '<a href=\"http://www.twitter.com\" rel=\"nofollow\">Twitter for BlackBerry</a>': 2, '<a href=\"http://www.google.com/\" rel=\"nofollow\">Google</a>': 2, '<a href=\"http://twitter.com/#!/download/ipad\" rel=\"nofollow\">Twitter for iPad</a>': 6, '<a href=\"http://linkis.com\" rel=\"nofollow\">Linkis.com</a>': 2, '<a href=\"http://rutracker.org/forum/viewforum.php?f=93\" rel=\"nofollow\">newzlasz</a>': 2, '<a href=\"http://ifttt.com\" rel=\"nofollow\">IFTTT</a>': 1, '<a href=\"http://www.myplume.com/\" rel=\"nofollow\">Plume\\xa0for\\xa0Android</a>': 1}\n"
     ]
    }
   ],
   "source": [
    "# Define count_entries()\n",
    "import pandas as pd\n",
    "tweets_df = pd.read_csv('tweets.csv')\n",
    "def count_entries(df, col_name='lang'):\n",
    "    \"\"\"Return a dictionary with counts of\n",
    "    occurrences as value for each key.\"\"\"\n",
    "\n",
    "    # Initialize an empty dictionary: cols_count\n",
    "    cols_count = {}\n",
    "\n",
    "    # Extract column from DataFrame: col\n",
    "    col = df[col_name]\n",
    "    \n",
    "    # Iterate over the column in DataFrame\n",
    "    for entry in col:\n",
    "\n",
    "        # If entry is in cols_count, add 1\n",
    "        if entry in cols_count.keys():\n",
    "            cols_count[entry] += 1\n",
    "\n",
    "        # Else add the entry to cols_count, set the value to 1\n",
    "        else:\n",
    "            cols_count[entry] = 1\n",
    "\n",
    "    # Return the cols_count dictionary\n",
    "    return cols_count\n",
    "\n",
    "# Call count_entries(): result1\n",
    "result1 = count_entries(tweets_df)\n",
    "\n",
    "# Call count_entries(): result2\n",
    "result2 = count_entries(tweets_df ,'source')\n",
    "\n",
    "# Print result1 and result2\n",
    "print(result1)\n",
    "print(result2)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Wow, you've just generalized your Twitter language analysis that you did in the previous chapter to include a default argument for the column name. You're now going to generalize this function one step further by allowing the user to pass it a flexible argument, \n",
    "that is, in this case, as many column names as the user would like!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'en': 97, 'et': 1, 'und': 2}\n",
      "{'en': 97, 'et': 1, 'und': 2, '<a href=\"http://twitter.com\" rel=\"nofollow\">Twitter Web Client</a>': 24, '<a href=\"http://www.facebook.com/twitter\" rel=\"nofollow\">Facebook</a>': 1, '<a href=\"http://twitter.com/download/android\" rel=\"nofollow\">Twitter for Android</a>': 26, '<a href=\"http://twitter.com/download/iphone\" rel=\"nofollow\">Twitter for iPhone</a>': 33, '<a href=\"http://www.twitter.com\" rel=\"nofollow\">Twitter for BlackBerry</a>': 2, '<a href=\"http://www.google.com/\" rel=\"nofollow\">Google</a>': 2, '<a href=\"http://twitter.com/#!/download/ipad\" rel=\"nofollow\">Twitter for iPad</a>': 6, '<a href=\"http://linkis.com\" rel=\"nofollow\">Linkis.com</a>': 2, '<a href=\"http://rutracker.org/forum/viewforum.php?f=93\" rel=\"nofollow\">newzlasz</a>': 2, '<a href=\"http://ifttt.com\" rel=\"nofollow\">IFTTT</a>': 1, '<a href=\"http://www.myplume.com/\" rel=\"nofollow\">Plume\\xa0for\\xa0Android</a>': 1}\n"
     ]
    }
   ],
   "source": [
    "# Define count_entries()\n",
    "def count_entries(df, *args):\n",
    "    \"\"\"Return a dictionary with counts of\n",
    "    occurrences as value for each key.\"\"\"\n",
    "    \n",
    "    #Initialize an empty dictionary: cols_count\n",
    "    cols_count = {}\n",
    "    \n",
    "    # Iterate over column names in args\n",
    "    for col_name in args:\n",
    "    \n",
    "        # Extract column from DataFrame: col\n",
    "        col = df[col_name]\n",
    "    \n",
    "        # Iterate over the column in DataFrame\n",
    "        for entry in col:\n",
    "    \n",
    "            # If entry is in cols_count, add 1\n",
    "            if entry in cols_count.keys():\n",
    "                cols_count[entry] += 1\n",
    "    \n",
    "            # Else add the entry to cols_count, set the value to 1\n",
    "            else:\n",
    "                cols_count[entry] = 1\n",
    "\n",
    "    # Return the cols_count dictionary\n",
    "    return cols_count\n",
    "\n",
    "# Call count_entries(): result1\n",
    "result1 = count_entries(tweets_df, 'lang')\n",
    "\n",
    "# Call count_entries(): result2\n",
    "result2 = count_entries(tweets_df, 'lang', 'source')\n",
    "\n",
    "# Print result1 and result2\n",
    "print(result1)\n",
    "\n",
    "print(result2)"
   ]
  },
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